1. Field of the Invention
The present invention relates to a light pen, a photo detective liquid crystal display device, and a display device having the light pen
2. Description of the Related Art
Display devices may be divided into a cathode ray tube (CRT) type display device, an electroluminescent display device (ELD) and a liquid crystal display (LCD) device.
A first type display device receives video signals from an information-processing device and converts the video signals so as to display an image. The first type display device communicates with the information-processing device in a one-way fashion. A user inputs data into the information-processing device by means of input devices such as keyboard, keypad and mouse, etc.
A second type display device receives first video signals from an information processing device, converts the first video signals so as to display an image, and also outputs signals inputted onto the screen of the display device by the user to the information processing device. In other words, the second type display device communicates with the information-processing device in a two-way fashion.
The second type display device further includes a touch panel so as to perform the two-way communication. The touch panel detects the pressure generated by a hand of the user or a touch pen, and outputs position data to the information-processing device. The position data designates the position of the point to which the pressure are applied. A selected position is perceived via the touch panel. The information-processing device receives the position data, generates second video signals using the position data, and outputs second video signals to the second type display device.
However, the second type display device has an increased thickness and weight due to the touch panel so as to communicate with the information-processing device in the two-way fashion. The second type display device using the touch panel may not display minute images and characters.
A third type display device senses the light inputted from the user, communicates with the information processing device in the two-way fashion, and outputs minute images and characters to the information processing device. The third type display device has a plurality of photo sensors. The photo sensors have a minute size and are arranged in a matrix shape. The display device transforms the light detected by the photo sensors into a signal so that the information-processing device is able to perceive the signal corresponding to the light detected by the photo sensors, and outputs the signal to the information-processing device. The information-processing device outputs a new video signal to the display device in response to the signal received from the display device. The display device displays a new image in response to the new video signal.
The user applies the light to the photo sensors of the display device by means of a light pen. The conventional light pen generates the light only when the light pen applies more than a predetermined pressure to the surface of the display device so as to reduce power consumption of the light pen.
The conventional light pen consumes little power. However, the user should always apply more than a predetermined pressure to the surface of the display device by means of the conventional light pen. Therefore, the user may feel fatigued when the user presses the surface of the display device by means of the conventional light pen for a long time. In addition, the display device may be scratched and damaged by the light pen. In addition, the conventional light pen has lens and have a complicated configuration. Therefore, the cost for manufacturing the light pen may increase, and the weight and volume of the light pen may increase. Further, the photo sensors may mistake an external light for the light generated from the light pen, so that the display device may operate in the wrong way.